I don't think you understand how elections work in the United States. He's right and you're wrong on this one. That you're using this as an example of cognitive dissonance is quite ironic.

The relevant difference is about 44,000 votes in three key states: https://www.npr.org/2020/12/02/940689086/narrow-wins-in-these-key-states-powered-biden-to-the-presidency

Doesn't matter which side you're on politically--if you don't know this, or don't know how it works, you're not going to be properly engaged next election (and you might, in the meantime, be saying some pretty stupid stuff).